This proposed K-01 career development award explores patterns of concurrent sexual partnerships, or partnerships that overlap in time, among urban African Americans in Philadelphia. I am an Assistant Professor of Medicine (Research) in the Division of Infectious Diseases at Brown University Medical School. I hope to use the K-01 award to transition from health policy to behavioral and social science research in HIV/AIDS prevention. My long-term career goals are to pursue an academic career in order to conduct behavioral and sociological research in the field of HIV/AIDS, to publish articles in the peer- reviewed literature, and conduct HIV/AIDS research that influences public policy. I hope to use the K01 award to learn how to conduct community-based participatory research (CPBR), develop new quantitative skills for behavioral science research, acquire expertise in behavioral research for HIV prevention and HIV intervention research, and gain expertise in health disparities research and ethical conduct of research in underserved populations. The research components of my application follow: Community-based participatory research (CBPR) approaches will be employed to explore 32-40 African American community leaders' opinions and knowledge about sexual concurrency and other factors contributing to HIV health disparities among urban African Americans. CBPR will also be used to examine African American community leaders' interest in developing and piloting novel interventions to address concurrent sexual relationships and other factors contributing to HIV health disparities among African Americans. Subsequently, differential rates of sexual concurrency and other factors that may contribute to racial disparities in HIV rates among African Americans testing for HIV in Philadelphia will be explored. This analysis will rely on secondary survey data collected during Philadelphia's rapid testing campaign, which tests approximately 6,000 people annually. The beliefs, attitudes, practices, patterns and causes of concurrent sexual partnerships will then be explored through 80 in-depth qualitative interviews among HIV- negative African American men and women testing for HIV in Philadelphia. In keeping with the CBPR framework guiding this study, the findings of each of the aforementioned research projects will be shared and explored with African American community leaders and the Philadelphia community at large. Community input about the study findings, appropriate interpretations, interventions, and public policy suggestions will be solicited. The findings from the aforementioned studies will then be used to design an R01 grant application proposing an HIV prevention intervention. The intervention will combine behavioral and social interventions to address concurrent sexual partnerships, and may aim to increase condom use rates with main and non-main partners, reduce concurrent sexual partners, or address other factors contributing to HIV health disparities among HIV-negative African Americans.